From c86b19f1ef262eeb1992a91879b38ffbed07a1a7 Mon Sep 17 00:00:00 2001 From: AurelienFT Date: Tue, 11 Jun 2024 21:56:14 +0200 Subject: Add lint to check manual pattern char comparison and merge its code with single_char_pattern lint --- clippy_lints/src/string_patterns.rs | 227 ++++++++++++++++++++++++++++++++++++ 1 file changed, 227 insertions(+) create mode 100644 clippy_lints/src/string_patterns.rs (limited to 'clippy_lints/src/string_patterns.rs') diff --git a/clippy_lints/src/string_patterns.rs b/clippy_lints/src/string_patterns.rs new file mode 100644 index 00000000000..64b5b8f9f27 --- /dev/null +++ b/clippy_lints/src/string_patterns.rs @@ -0,0 +1,227 @@ +use std::ops::ControlFlow; + +use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then}; +use clippy_utils::eager_or_lazy::switch_to_eager_eval; +use clippy_utils::macros::matching_root_macro_call; +use clippy_utils::path_to_local_id; +use clippy_utils::source::{snippet, str_literal_to_char_literal}; +use clippy_utils::visitors::{for_each_expr, Descend}; +use itertools::Itertools; +use rustc_ast::{BinOpKind, LitKind}; +use rustc_errors::Applicability; +use rustc_hir::{Expr, ExprKind, PatKind}; +use rustc_lint::{LateContext, LateLintPass}; +use rustc_middle::ty; +use rustc_session::declare_lint_pass; +use rustc_span::{sym, Span}; + +declare_clippy_lint! { + /// ### What it does + /// Checks for manual `char` comparison in string patterns + /// + /// ### Why is this bad? + /// This can be written more concisely using a `char` or an array of `char`. + /// This is more readable and more optimized when comparing to only one `char`. + /// + /// ### Example + /// ```no_run + /// "Hello World!".trim_end_matches(|c| c == '.' || c == ',' || c == '!' || c == '?'); + /// ``` + /// Use instead: + /// ```no_run + /// "Hello World!".trim_end_matches(['.', ',', '!', '?']); + /// ``` + #[clippy::version = "1.80.0"] + pub MANUAL_PATTERN_CHAR_COMPARISON, + style, + "manual char comparison in string patterns" +} + +declare_clippy_lint! { + /// ### What it does + /// Checks for string methods that receive a single-character + /// `str` as an argument, e.g., `_.split("x")`. + /// + /// ### Why is this bad? + /// While this can make a perf difference on some systems, + /// benchmarks have proven inconclusive. But at least using a + /// char literal makes it clear that we are looking at a single + /// character. + /// + /// ### Known problems + /// Does not catch multi-byte unicode characters. This is by + /// design, on many machines, splitting by a non-ascii char is + /// actually slower. Please do your own measurements instead of + /// relying solely on the results of this lint. + /// + /// ### Example + /// ```rust,ignore + /// _.split("x"); + /// ``` + /// + /// Use instead: + /// ```rust,ignore + /// _.split('x'); + /// ``` + #[clippy::version = "pre 1.29.0"] + pub SINGLE_CHAR_PATTERN, + pedantic, + "using a single-character str where a char could be used, e.g., `_.split(\"x\")`" +} + +declare_lint_pass!(StringPatterns => [MANUAL_PATTERN_CHAR_COMPARISON, SINGLE_CHAR_PATTERN]); + +const PATTERN_METHODS: [(&str, usize); 22] = [ + ("contains", 0), + ("starts_with", 0), + ("ends_with", 0), + ("find", 0), + ("rfind", 0), + ("split", 0), + ("split_inclusive", 0), + ("rsplit", 0), + ("split_terminator", 0), + ("rsplit_terminator", 0), + ("splitn", 1), + ("rsplitn", 1), + ("split_once", 0), + ("rsplit_once", 0), + ("matches", 0), + ("rmatches", 0), + ("match_indices", 0), + ("rmatch_indices", 0), + ("trim_start_matches", 0), + ("trim_end_matches", 0), + ("replace", 0), + ("replacen", 0), +]; + +fn check_single_char_pattern_lint(cx: &LateContext<'_>, arg: &Expr<'_>) { + let mut applicability = Applicability::MachineApplicable; + if let Some(hint) = str_literal_to_char_literal(cx, arg, &mut applicability, true) { + span_lint_and_sugg( + cx, + SINGLE_CHAR_PATTERN, + arg.span, + "single-character string constant used as pattern", + "consider using a `char`", + hint, + applicability, + ); + } +} + +fn get_char_span<'tcx>(cx: &'_ LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option { + if cx.typeck_results().expr_ty_adjusted(expr).is_char() + && !expr.span.from_expansion() + && switch_to_eager_eval(cx, expr) + { + Some(expr.span) + } else { + None + } +} + +fn check_manual_pattern_char_comparison(cx: &LateContext<'_>, method_arg: &Expr<'_>) { + if let ExprKind::Closure(closure) = method_arg.kind + && let body = cx.tcx.hir().body(closure.body) + && let Some(PatKind::Binding(_, binding, ..)) = body.params.first().map(|p| p.pat.kind) + { + let mut set_char_spans: Vec = Vec::new(); + + // We want to retrieve all the comparisons done. + // They are ordered in a nested way and so we need to traverse the AST to collect them all. + if for_each_expr(cx, body.value, |sub_expr| -> ControlFlow<(), Descend> { + match sub_expr.kind { + ExprKind::Binary(op, left, right) if op.node == BinOpKind::Eq => { + if path_to_local_id(left, binding) + && let Some(span) = get_char_span(cx, right) + { + set_char_spans.push(span); + ControlFlow::Continue(Descend::No) + } else if path_to_local_id(right, binding) + && let Some(span) = get_char_span(cx, left) + { + set_char_spans.push(span); + ControlFlow::Continue(Descend::No) + } else { + ControlFlow::Break(()) + } + }, + ExprKind::Binary(op, _, _) if op.node == BinOpKind::Or => ControlFlow::Continue(Descend::Yes), + ExprKind::Match(match_value, [arm, _], _) => { + if matching_root_macro_call(cx, sub_expr.span, sym::matches_macro).is_none() + || arm.guard.is_some() + || !path_to_local_id(match_value, binding) + { + return ControlFlow::Break(()); + } + if arm.pat.walk_short(|pat| match pat.kind { + PatKind::Lit(expr) if let ExprKind::Lit(lit) = expr.kind => { + if let LitKind::Char(_) = lit.node { + set_char_spans.push(lit.span); + } + true + }, + PatKind::Or(_) => true, + _ => false, + }) { + ControlFlow::Continue(Descend::No) + } else { + ControlFlow::Break(()) + } + }, + _ => ControlFlow::Break(()), + } + }) + .is_some() + { + return; + } + span_lint_and_then( + cx, + MANUAL_PATTERN_CHAR_COMPARISON, + method_arg.span, + "this manual char comparison can be written more succinctly", + |diag| { + if let [set_char_span] = set_char_spans[..] { + diag.span_suggestion( + method_arg.span, + "consider using a `char`", + snippet(cx, set_char_span, "c"), + Applicability::MachineApplicable, + ); + } else { + diag.span_suggestion( + method_arg.span, + "consider using an array of `char`", + format!( + "[{}]", + set_char_spans.into_iter().map(|span| snippet(cx, span, "c")).join(", ") + ), + Applicability::MachineApplicable, + ); + } + }, + ); + } +} + +impl<'tcx> LateLintPass<'tcx> for StringPatterns { + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if !expr.span.from_expansion() + && let ExprKind::MethodCall(method, receiver, args, _) = expr.kind + && let ty::Ref(_, ty, _) = cx.typeck_results().expr_ty_adjusted(receiver).kind() + && ty.is_str() + && let method_name = method.ident.name.as_str() + && let Some(&(_, pos)) = PATTERN_METHODS + .iter() + .find(|(array_method_name, _)| *array_method_name == method_name) + && let Some(arg) = args.get(pos) + { + check_single_char_pattern_lint(cx, arg); + + check_manual_pattern_char_comparison(cx, arg); + } + } +} -- cgit 1.4.1-3-g733a5